How remains of the first emperor's workers fuel a modern political controversy

East of the famed terracotta warriors in Xi'an, archaeologists found the remains of workers who built the mausoleum complex of China's first emperor, Qin Shihuangdi. They were buried haphazardly, but showed no obvious cause of death other than exhaustion. (Courtesy Duan Qingbo, Shaanxi Provincial Institute of Cultural Relics and Archaeology, Xi'an, China)

From a distance, the mausoleum of China's first emperor, Qin Shihuangdi, looks like a verdant hill, a welcome resting place among craggy peaks. According to the Han Dynasty historian Sima Qian, the unopened 2,200-year-old tomb contains countless treasures, including replicas of palaces and rivers of mercury. Other parts of the memorial complex in Xi'an have yielded incredible finds--most famously, a life-size terracotta army 8,000 strong. Writing a century after the emperor's death in 210 B.C., Sima Qian wrote that it took more than 700,000 workers to complete the massive project. Though some scholars argue that his number is inflated--greater than the population of any city in the world at the time--it remains widely used by Chinese historians.

Even if the true number of workers at the emperor's tomb was a fraction of that, they still represent a large and largely unknown population. Who were they? Where did they come from? Knowing their origins could tell archaeologists and historians a great deal about labor resources, movement, and migration during an important period, when Qin Shihuangdi sought to expand his newly unified nation.

"There has been little historical evidence about where the mausoleum workers came from," says Xu Zhi, a doctoral candidate in molecular anthropology at Fudan University in Shanghai. "To date, most people have believed they were from the north of China." Epitaphs from the period suggest the workers came from the northern region surrounding the emperor's tomb. This area includes what were once the other warring states unified under the emperor's rule, says Duan Qingbo, former head of the Qin Shihuangdi Mausoleum Excavation Team, now a professor at Xi'an's Northwest University.

DNA from a grave site for the tomb workers is now providing hints that they came from much farther afield. Yet DNA evidence, which often seems so clear and definitive, can be anything but, especially in China, where a lack of scientific transparency and concerns about the politicization of results have plagued recent efforts to provide a genetic perspective to ancient questions.